Tower cranes are well known in the construction of high rise buildings. Depending on their size, tower cranes are used in the construction of medium to high rise buildings and the like structures. There generally is high tower standing at the side of the building site and taller than the anticipated site of the building. This tower crane has a long boom with a trolley thereon. The length of the boom must be longer than the proposed width of the building to be able to reach all corners of the building. A shorter end of the boom receives weights to balance the boom with a load at the other end. The weight cannot exceed a certain measure so that the boom stays somewhat balanced without a load and the load to be hoisted cannot exceed a certain measure to avoid overcoming the balancing load on the boom at the shorter end. This a very costly and time consuming operation when constructing a building of great heights.